Powder spraying apparatus and method



April 16, 1957 F. T. WARD POWDER SPRAYING APPARATUS AND METHOD Filed Nov. '7, 1955 iLN Fl INVENTOR.

FRANK T. WARD ywz HIS ATTORNEY.

United States Patent POWDER SPRAYDIG APPARATUS AND METHOD Frank '1. Ward, Wilton, Comm, assignor to James V.

Taylor, Charles E. Morgan, and Robert C. Read, cpartners doing business under the trade name and style of Rockport Industries, Montreal, Quebec, Canada Application November 7, 1955, Serial No. 545,173

4 Claims. (Cl. 302-52) This invention relates to an improved apparatus and method for incorporating finely divided material into an air stream in order that the material may be deposited uniformly over surfaces.

An important object ofthe invention is to provide an apparatus including a supply tank for the powder material and wherein there is a substantially uniform concentration of the material in the air line from the start of the operation when the tank is filled to its normal capacity until the tank has become exhausted and a new tank is cut into the air line.

The method and apparatus of the present invention has particular application to the baking industry wherein it has long been known that extremely fine starch is far superior to flour as a dusting agent. Much less starch than flour is required for this purpose and the present method applies the starch dust in controlled minimum amounts needed, thereby avoiding the excessive waste of flour and contamination of bakery plant air that now occurs.

Another object of the present invention is to provide an apparatus which can operate with a floor level tank for the powdered material, thus eliminating an important objection to the older gravity feed devices where it was necessary to manually carry buckets of the material to an elevated tank. Another objection to the gravity feed devices lay in the lack of uniformity of dispersion of the powder in the air stream, the system having a tendency to deliver more powder to the stream when the tank was full and progressively less as the tank became empty.

The same condition exists in the non-gravity systems, the reason being that the volume of the air chamber above the powder was a definite factor in the quantity of powder dispersed in the stream. The volume of this chamber, which is the air and powder mixing chamber, of necessity had to increase as the powder supply diminished in the tank.

The novel feature in the present invention resides in the provision of an air chamber above the powder having a constant volume regardless of the quantity of powder in the tanks. This desirable result is accomplished by means of an inverted powder pick-up cone which is suspended at the lower end of an extensible tubular member which affords a desired measure of support for the cone so that its lower annular edge lies embedded slightly below the level of the powder and it descends as the powder is consumed. The outside diameter of the cone is only slightly less than the inside diameter of the tank and the powder lying outside the lower rim of the cone forms a highly effective seal between the interior of the cone which is the air and powder mixing chamber and the chamber above the cone. The pressures in the two chambers are about the same but the important thing is that the internal volume of the cone is unaifected by the increase in volume above the cone.

The figure in the drawing shows a front elevation of the apparatus of the present invention, parts being shown in section.

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A suitable fiat mounting base 1 is provided having four leveling screws 2, one at each corner of the base. A control mast 3 may comprise a hollow stainless steel pipe which is rigidly mounted on base 1 in a socket 4 secured thereto by bolts 6. The upper end of mast 3 is closed by means of cap 5 which is suitably secured in place on the mast.

Slightly below cap 5 a cock 7 and a strainer-filter 8 are suitably supported on mast 3. The latter is provided with a bleed valve 8' to remove any moisture that may be trapped therein. Normally these elements will be mounted to the rear of the mast but for clarity in the drawing they are shown to the left of the mast.

Cock 7 is provided at its inlet opening 9 with means such as a pipe thread to permit attachment of a pipe or hose from the plant compressed air supply to furnish operating air pressure for the machine. The outlet opening of cock 7 is connected to the inlet opening of strainerfilter 8 by a pipe nipple. The outlet opening of strainerfilter 8 is in turn connected by pipe 10 through an opening in the wall of mast 3 to one horizontal opening in a pipe fitting. The other horizontal opening of this fitting is connected by a nipple passing out through an opening in the wall of mast 3 to an air pressure gauge 11 located preferably at the front of the mast.

The third opening of the fitting points vertically downwardly inside mast 3 and is connected by pipe 12 directly to the inlet opening of air pressure regulating valve 13, whose operating stem passes through an opening in the wall of mast 3 and is fitted with an operating knob 14 located on the front side of the mast vertically below gauge 11.

The outlet opening of pressure regulating valve 13 is connected by pipe 15 to the upper vertical opening of a pipe fitting. The horizontal opening of this fitting is connected by a pipe passing through an opening in the wall of mast 3 vertically below knob 14 to one horizontal opening of a second pipe fitting outside the mast. The vertical outlet of this second pipe fitting is provided with a safety valve 16 and the other horizontal opening of this fitting connects with an air pressure gauge 17.

The lower vertical opening of the first fitting inside the mast is connected by pipe 18 inside mast 3 to the inlet opening of a three way valve 19, whose operating stem passes through an opening in the wall of mast 3 and is provided with an operating handle 20 which is located on the front of mast below pressure gauge 17. Operating handle 20 has three positions. When in the vertical position shown no air can pass through the valve. When moved to its left position air can pass from vertical pipe 18 through the left opening of three way valve only. Similarly when handle 20 is moved to the right air can pass from pipe 18 only through the right opening of three way valve 19.

The left and right outlets of three way valve 19 are rovided with elbows 21 and 21', respectively, opening downwardly inside mast 3 and are connected with pipes 22 and 22', respectively, which lead downwardly inside the mast to a point just above pipe socket 4 where each is connected with a pipe elbow 23.

Pipe elbow 23 is fitted with a horizontal pipe nipple 24 which passes through an opening in mast 3 and connects with pipe union 25.

Pipe union 25 is connected by pipe 26 through an opening in tank skirt 27. Pipe 26 is fitted to elbow 28 located immediately below the center of the bottom of a tank 30, two of which are shown mounted on the base. Elbow 28 is fitted to a vertical pipe nipple 29 welded or brazed at 31 into the bottom of tank 30.

Each tank 30 consists of a drawn steel sheet having an integral rounded bottom. The walls and bottom are smooth and should be formed without welds or welding beads. Each of tanks is also equipped with a polished metal cone 32 whichis sealed air tight at its upper rim 33 to tank shell 31 andat its bottom by a nut 34 and washer 35 which screws on-the upper end of pipe nipple 29.' A pipe cap 36 is drilled to form aspecific size of'orifice 37 and is fitted to pipe nipple 29 above and"free of nut 34. This cap is readily removable to allow for substitution of another having a different orificefor a different particle size or material.

Each tank 30 has a domed steel cover 40 hinged at the upper end thereof and fitted with a gasket 41 and with screw clamps 42- equally spaced around the rim of the cover whereby the cover may be sealed air tight to. the-tank. A pipe nipple 43-is brazed or welded through; the center of each tank cover. To the lower end of each pipe nipple 43 is fitted an accordion shaped, extensible,: flexible, electrically conductive, synthetic rubber hose 44. To the lower end ofthis hose is suitably attached an inverted powder pick-up cone 45 made of light material and having a diameter at its larger end substantially one-quarter inch. smaller than the inside diameter of tank 31 A ring47 mounted above the cone 45 by means of a spider 48 serves to retain the cone in a horizontal position as it descends. The accordion hose 44,:which contains no spring, serves to permit cone 45 to rest without restraint on the surface of the powder, whose upper level is shownat 46, in the tank and to drop freely with the falling surface of the powder as it is consumed during machine operation. Flexible hose 44 also permits removal of pick-up cone 45 from tank 30 whenever it is necessary to refill the tank. Hose 44, being electrically conductive, serves to carry any static that maybe generated to the metal cover of the tank and thence to ground through a ground wire (not shown). Normally, when the machine is in operation, cone 45 embeds itself slightly below the powder surface and maintains this relative position as the level of the powder falls.

The outside end of pipe nipple 43 is fitted with a removable cap 50 having an orifice pipe nipple 51, to which is attached flexible transparent hose 52 which has sufficient length to allow the'free opening and closing of the tank cover, its other end being attached to pipe nipple 53, which passes horizontally through a hole in the mast and into the'interior thereof, where it is fitted with a pipe'elbow 54. This elbow is in turn connected to a pipeSS risingwertically inside the'mast and passing through a suitable-hole in cap 5.

Pipes-orhosesS'l' andSSare attached to the exposed upper ends of pipes 55 and 56, respectively, and serve to conduct the mixture of powder and air from either tank to thedusting hoods where it is to be applied to the plant product.

The'operation of the apparatus is as follows. After checking the 'valves and gauges the air supply is turned onand gauge 17 is set at the pressure reading necessary to deliver powder to the dusting hoods at a rate which will properly dust the surface or product. The arrangement shown in the drawing is particularly suited to the starch dusting of dough in bakeries and the range of air pressure at the outletside of pressure regulating valve 13 is from i p. s. i. to 3 'p. s. i. for a delivery rate of 8 to 30 pounds per hour of starch powder at the dusting hoods. The operator can at all times determine that powder is flowing by examining transparent hose 52. It is next necessary to wait until the powder supply is depleted before cutting in a new tank.

Powder pick-up 'cone 45 serves three major purposes. First it provides a constant volume air and powder mixing chamber to insure uniform mixing of powder and air from a fully charged tank all the way down to 'a' from the initial'escapeof some powder upward past the cone rim into the space above the cone, which powder promptly settles'down to form a sealing ring of powder above and around the rim of the cone against the tank wall, the internal volume of the cone remains unaffected by the increasing volume of space above the cone as the powder level falls, the cone-remaining free to fall with the falling powder surface. This floating seal of powder on the upper side of the'cone rim also automatically ermits equalization of the pressure in the tank above and below the cone but without destroying the effective ness of the seal. The result of these automatic actions is that the rate of powder delivery from charged tank to exhausted tank remains substantially constantfor any fixed air pressure applied to the powder at the tank bottom air inlet, thereby permitting accurate rates of powder delivery for specific air pressure settings. Thirdly, the volume and weight chosen for cone 45 in conjunction with the size of orifices 37 and 51 determine, for any desired range of rates of powder delivery, the range of air pressures required to provide such powder delivery rates.

In connection with the novel action of cone 45 it may be pointed out that in general it is desirable to deliver the powder to the object or surface to be covered in the form of a gently moving-cloud from which the powder falls by gravity as much as by'velocity on to the object or surface, rather than for the powder to be very forcefully sprayed against the object. In addition, this gentle application'of the powder does much to avoid escape of excess power into the atmosphere of the room. Dust collection equipment is normally required at actual points where the powder is applied, i. e., the dusting hoods, but obviously the less excess powder required the less will be the possibility of room air pollution.

The ring'47 mounted above the cone 45 by means of spider 48 serves to retain the cone in a horizontal position as it descends. This ring has substantially the same diameter as the cone and the ring and cone are thus two elements of an imaginary cylinder of lesser diameter than the tank. These elements, in combination, prevent' tipping of the cone during downward travel which could occur if the tank has any interior welding beads.

It will be appreciated from the foregoing description that the powder lying on the inside and outside of the cone above the lower edge thereof has a rather peculiar action in that it acts asa seal to prevent general and free interchange of air and entrained powder between the vacuum above and below the cone, yet permits an occasional automatic balancing of air pressure above and below the cone. In other words, the unusual action of this powder seal in addition to the natural shape of the inverted cone serves to produce a substantially fixed ratio of powder to air in the lower portion of the tank and positively directs the powder toward the outlet while preventing any appreciable powder pickup by the air stream in the space above the cone, and it does this by permitting a periodic and continuing balancing of the air pressure below and above the cone without the transfer of air being of such high velocity as to permit it to carry any high concentration of powder into the upper chamber. The action of the pickup cone is, in eifect, that of a piston with a sealing means that acts like a discriminating membrane in that it confines a mixture of powder and fluid to the space below the piston but permits the transporting fluid only to pass the piston into the space above the piston. In other words, there are two chambers separated by a peculiar piston which permits violent and directed turbulence in the lower chamber but insures no turbulence in the upper chamber while maintaining an equalized air pressure in both chambers despite progressive relative volume change in both chambers.

While there have been described herein what are at present considered preferred embodiments of the invention, it'will be obvious to those skilled in the art that many modifications and changes may be made therein without departing from the essence of the invention. It is therefore to be understood that the exemplary embodiments are illustrative and not restrictive of the invention, the scope of which is defined in the appended claims, and that all modifications that come within the meaning and range of equivalency of the claims are intended to be included therein.

What I claim is:

1. Apparatus for spraying powder comprising a closed tank having a lower section to receive the powder and which is provided with an inlet port for air under regulated pressure, an inverted powder pick-up cone carried on the mass of powder with its lower annular edge imbedded below the powder level, the cone being of slightly lesser diameter than the tank and being freely movable downwardly therein as the powder level descends, said cone forming an air and powder mixing chamber which is effectively sealed from the varying volume above the cone by powder lying above and outside said annular edge and whose volume remains substantially unaffected as the powder level descends, an extensible tubular support connected with the cone and communicating with the inside thereof and supported at its upper end on the upper wall of the tank, and a conduit connected with the tubular support for the air and powder mixture.

2. Apparatus for spraying powder comprising a tank for the powder and having a conical shaped lower section which is provided with an inlet port for air under regulated pressure, a removable cover at the upper end of the tank, an inverted powder pick-up cone carried on the mass of powder with its lower :annular edge imbedded below the powder level, the cone being of slightly lesser diameter than the tank and being freely movable downwardly therein as the powder level descends, said cone forming an air and powder mixing chamber which is efiectively sealed from the upper section of the tank by powder lying above and outside said annular edge and whose effective volume remains substantially constant as the powder level descends, an extensible tubular support connected with the cone and communicating with the interior thereof and supported at its upper end on the upper wall of the tank and a conduit connected with the tubular support for the air and powder mixture.

3. An apparatus for spraying powder comprising a closed tank having a lower section to receive the powder and an upper section forming an air chamber, an inverte'd powder pick-up cone of slightly lesser diameter than the chamber and arranged to pass freely downwardly therein as the powder is consumed and with its lower annular edge lying below the powder level, an inlet port at the lower end of the tank for the admission of air under regulated pressure, an extensible tubular support connected with the interior of the cone in its downward travel and secured at its upper end to the upper wall of the tank, the cone forming an air and powder mixing chamber whose volume remains substantially unchanged as the powder level descends, said air within the mixing chamber limiting downward travel of said lower edge in the powder mass, and a conduit connected with the tubular support for the air stream with the powder incorporated therein.

4. An apparatus for spraying powder comprising a closed tank having a lower section to receive the powder and an upper section forming an air chamber, an inverted powder pick-up cone of slightly lesser diameter than the chamber and arranged to pass freely downwardly therein as the powder is consumed while its lower annular edge lies below the powder level, an inlet port at the lower end of the tank for the admission of air and means for regulating pressure of the air, an extensible tubular support connected with the interior of the cone in its downward travel, a ring secured above the cone to prevent tipping movement of the cone during its downward travel, the cone forming an air and powder mixing chamber whose volume remains substantially unaffected as the powder level descends, said air within the mixing chamber limiting downward travel of said lower edge in the powder mass, and a conduit connected with the tubular support for the air stream passing out of the mixing chamber with the powder incorporated therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,349,751 Cross Aug. 17, 1920 2,255,438 Robinson Sept. 9, 1941 

